I would jump into a scripting language like Python, Ruby or Lua. I am biased towards Python though since I have been digging into web development with Django and game programming with pyglet.

I would also look at functional languages like Haskell or Scala.

It really comes down to what type of programming you want to do or what type interests you. But generally I usually suggest that people learn at least 3+ languages (More the better in my opinion) and try and learn different styles of programming like Dynamic, Static, Functional, ECT.

as in to get a job : languages like .Net , PHP etc. are also in quite demand.

useful

as in you want to know different languages and programming paradigms then there's Lisp(or Scheme),Haskell
etc.

good, and useful programming languages

No programming language is bad or useless they are good for what they were meant to be , whereas languages like C++ tend be more general and applicable for most uses.(even languages like Brainf*ck are good at what they were meant for i.e. give some pain on head :D)